IT is very simple to change the texture. They are located in the UI foider and have the extension .DDS. All you need is to download the plug-in for Photoshop, so you can open this file type. Highly recommend you make backups of modified files, or if you did something wrong, the game can crash. Good Luck

It's simple
1) Download the plug-in format .DDS for Photoshop, so it can open, edit and save DDS files. Set in Photoshop (I use CS3)
2) All the .DDS files are located in the UI folder, which is located in the root folder of the Game. Open, for example, main.DDS
3) Wiil see a lot of menus. They can be painted (just brush or change the brightness, contrast), change the transparency (apply the alpha channel of varying density or make invisible all by putting an alpha channel 100% density). You can open the other .DDS files and see what they contain
4) Save

VERY IMPORTANT
1) Before setting up the changed files should be completely off the client and make back-up copy of the original files, which will be replaced
2) If you open a .DDS file in Photoshop and see a message, that "this file contains the MIP MAPS- open whith existing MIP MAPS?"- you need to click OK, change file as you like and when saving this file, don't change anything in options of saving- just put a checkmark in the "Use existing MIP MAPS" option
3) If you open a .DDS file in Photoshop and there is no message, change file as you like and when saving this file, don't change anything in options of saving- just put a checkmark in the "NO MIP MAPS" option
4) Do not change the resolution and size of files

For example, I can create 2-3 themes interface, so that all can see what you can do. Create your own unique theme- everyone can))